CALCIUM IN AGRICULTURE
Calcium is a chemical element, symbol Ca, atomic number 20 (20 protons and 20 electrons) and atomic mass 40 u. It is a family of alkali earth metal belonging to the group 2 of the periodic table of the chemical elements.
CALCIUM SOURCES
Calcium is the fifth element in abundance in the earth's crust. It is found in native state in nature, being always as constituents of rocks or minerals such as those containing carbonates (marble, calcite, limestone and dolomite) and sulfates (gypsum, alabaster), fluorite (fluoride), apatite (calcium fluorophosphate) and granite (silicate rocks).
CALCIUM IN AGRICULTURE
Calcium is a secondary macronutrients with magnesium (Mg) and sulfur (S). The indirect effects of calcium are as important as its role as a nutrient. The calcium enhances root growth, promotes increased microbial activity, increased availability of molybdenum (Mo) and other nutrients.
PHYSIOLOGICAL FUNCTION
Calcium enzymatic functions involved in the phosphate transfer processes, such as the phospholipase. Constituent pectates, which are deposited in the middle lamella, giving resistance to cell walls. Constituent or activator of several enzymes such as alpha amylase and nucleases.
Calcium pectates is a component of the middle lamella, which is important for the occurrence of mitosis.
In the cytosol, Ca +2 occurs in minute amounts (-7 10 - 10 -8 M) having an important second messenger in signal function translational pathways, sometimes calmodulin with a binding to a protein which is activated by Ca (has 4 calcium binding sites) which in turn can activate enzymes.
Contrary to what occurs with most nutrients, calcium only moves through apoplast. Their entry in the root is therefore restricted to points where the streaks of Caspary not consolidated as occurs at the tips of roots or when the differentiation of secondary roots that form breaking the endoderm.
CALCIUM FORMS AVAILABLE AND ABSORPTION
The available forms of Ca ++ are adsorbed on soil colloids. By cation exchange, they pass into the soil solution are then absorbed by plants. This absorption occurs mainly by mass flow and minor by root interception. The majority of calcium is located in the cell walls.
CALCIUM DEFICIENCY SYMPTOMS IN PLANTS
The symptoms are:
- Death of the apical bud;
- Interveinal chlorosis and necrosis in younger leaves (deficiency symptoms in Ca +2 are more pronounced in young tissues, since practically nonexistent your transport in the phloem);
- Deformed and wound tissues are found in plants deficient;
- The empty pods in soybean and leaves rolled in corn are calcium deficiency symptoms;
- Slippery roots (no stiffness), or necrosis in new parts as in estilar rot of tomato, the distal part of the fruit, for lack of calcium in the soil or lack of transpiration stream (dry).